The People's Republic of China's first submarine design was the locally-produced derivative of the Romeo class
submarines provided to China by the Soviet Union. Large numbers of
these were built, but their obsolete design, derived from World War II
submarine technology, led China to develop a wholly new class on its
own, resulting in the Type 039.

Designed for attacking both other submarines and surface ships with torpedoes,
the submarine uses a modern teardrop-shape hull for underwater
performance. The hull incorporates four rudders and is propelled by a
single propeller. For quieter operation, the engine was mounted with
shock absorbers and the hull is plated in rubber tiles for sound
deadening. Development was not without problems, as a lengthy testing
period for the first vessel (320) attests. Problems with noise
levels and underwater performance led to revisions in the design and
only a single boat was ever built to the original specification.

Improvements led to the specification for the Type 039G, which
became the bulk of production, with seven of the type entering service.
Elimination of the stepped design for the conning tower is the primary
visual cue for identification of the G variant.

This class has three versions: the original Type 039, Type 039G and Type 039A. The most obvious visual difference between the three types is the conning tower. The Type 039's conning tower is stepped, rising aft. In an effort to shrink the submarine's acoustic signature, the Type 039G's conning tower was given a more conventional shape. The Type 039A
also has a conning tower of more conventional shape, but the tower
lacks the diving planes present on the conning towers of both the Type 039 and the Type 039G.

Primary weapon for the Type 039 is the 533 mm Yu-4 torpedo, a locally produced passive homing 40-knot (74 km/h) torpedo based on the SAET-50 and roughly comparable to the SAET-60.
Surface targets may be attacked at up to 15 km. Yu-6 wire-guided
torpedoes may also be used for targeting submarines. It is also likely
that the Type 039 is capable of carrying the YJ-8anti-ship missile, a cruise missile
which can be launched from the same tube as the boat's torpedoes, and
can target surface vessels at up to 80 km. The missile is subsonic and
carries a 165 kg warhead. For mining operations, in place of torpedoes,
the submarine can carry 24 to 36 naval mines,
deliverable through the torpedo tubes. The general designer of the
torpedo and missile launching system is Mr. Sun Zhuguo (孙柱国, 1937-), and
the launching system is compatible with AShM, ASW, torpedoes of both
China and Russian/Soviet origin.

Although Type 039 has successfully test fired the CY-1 ASW Missile under water like the Yuan-classsubmarine,
the status of the missile is in question because nothing is heard about
it entering mass production. The CY-1 ASW missile has a maximum range
of 18 km (10 nm), and when using A244 or Mark 46 torpedo as a payload.